Zero-length model

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Demos
Posts: 3
Joined: Tue Feb 19, 2013 1:51 am
Location: University of Cyprus

Zero-length model

Post by Demos » Tue Mar 26, 2013 6:43 am

to whom may help.
I have modelled four parallel zero-length elements connected with rigid-bars, and a static force is then applied at the end of a truss. When I try to analyse the model I get warnings which I cannot solve.
I will be grateful for any help that can be provided for my model!!!

#
wipe;
# Units: mm, N
file mkdir Data; # create data directory
model BasicBuilder -ndm 2 -ndf 3;
#
# Model assembly
# Define nodal coordinates:
node 1 0 0;
node 2 0 100;
node 3 0 103.4;
node 4 0 163.4;
node 5 0 223.4;
node 6 0 0;
node 7 0 100;
node 8 0 103.4;
node 9 0 163.4;
node 10 0 223.4;
node 11 490 100;
#
# Define Single point constraints -- Boundary Conditions
fix 1 1 1 1;
fix 2 1 1 1;
fix 3 1 1 1;
fix 4 1 1 1;
fix 5 1 1 1;
#
# equalDOF $rNodeTag $cNodeTag $dof1 $dof2 ...
equalDOF 1 6 2 3;
equalDOF 2 7 2 3;
equalDOF 3 8 2 3;
equalDOF 4 9 2 3;
equalDOF 5 10 2 3;
#
# geomTransf choice is Linear, Corotational, PDelta ;
geomTransf Linear 1;
#
# Define rigid links between nodes
# rigidLink $type(bar or beam) $masterNodeTag $slaveNodeTag
rigidLink bar 1 2;
rigidLink bar 2 3;
rigidLink bar 3 4;
rigidLink bar 4 5;
rigidLink bar 6 7;
rigidLink bar 7 8;
rigidLink bar 8 9;
rigidLink bar 9 10;
#
# Define UniaxialMaterials # Springs
# uniaxialMaterial MultiLinear $matTag $u1 $f1 $u2 $f2 $u3 $f3 $u4 $f4 ..
uniaxialMaterial MultiLinear 1 0.00 0 1.00 128766 2.00 166885 5.00 211706 10.00 231624 15.00 232813 20.00 22674; #plate in bearing
uniaxialMaterial MultiLinear 2 0.00 0 1.00 96575 2.00 125164 5.00 158780 10.00 176718 15.00 174610 20.00 17005; #Beam web in bearing
uniaxialMaterial MultiLinear 3 0.00 0 2.00 2000 2.20 37699 2.44 75398 3.04 113097 5.29 150796; #Bolts in shear
uniaxialMaterial Elastic 4 0.00 0 1.20 4691 2.40 9383 3.60 14074 16.0 0; #friction
uniaxialMaterial MultiLinear 5 0.00 0 1.00 0 2.00 0 5.00 0 10.00 100000000 15.00 100000000 20.00 100000000; #beam lower flange in contact with column
#
# uniaxialMaterial Steel01 $matTag $Fy $E0 $b
uniaxialMaterial Steel01 6 356 176350 0.5; # Beam UB 305x165x40
#
# Create one spring in each bolt row
#uniaxialMaterial Series $matTag $tag1 $tag2 ...
uniaxialMaterial Series 7 1 2 3;
uniaxialMaterial Parallel 8 7 4;
#
# Define zero length spring elements:
#element zeroLength $eleTag $iNode $jNode -mat $matTag1 $matTag2 ... -dir $dir1 $dir2 ...
element zeroLength 1 1 6 -mat 5 -dir 1
element zeroLength 2 3 8 -mat 8 -dir 1
element zeroLength 3 4 9 -mat 8 -dir 1
element zeroLength 4 5 10 -mat 8 -dir 1
#
# Define beam element
# element truss $eleTag $iNode $jNode $A $matTag
element truss 5 7 11 5130 6
#
# define output
recorder Node -file Data/cbmresults.out -time -node 11 -dof 2 disp; # displacements of free nodes
#
# apply load
pattern Plain 1 Linear {
load 11 5000 -5000 0.;
};
#
# analysis commands
integrator LoadControl 0.001
test NormDispIncr 1.0e-4 10 1
algorithm Newton
numberer Plain
constraints Transformation 1.0
system BandGeneral
analysis Static
analyze 10
loadConst -time 0.0;
#
puts "Done!"

fmk
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Posts: 5866
Joined: Fri Jun 11, 2004 2:33 pm
Location: UC Berkeley
Contact:

Re: Zero-length model

Post by fmk » Mon Apr 01, 2013 2:48 pm

it failed because your system of equation failed in the solve .. this typically means you have not enough constraints.

Demos
Posts: 3
Joined: Tue Feb 19, 2013 1:51 am
Location: University of Cyprus

Re: Zero-length model

Post by Demos » Mon Apr 08, 2013 9:33 am

can you give me some guidance in order to fix this error? I have fixed some nodes, i.e. 1,2,3,4,5, do I have to put restraints to other nodes too??

fmk
Site Admin
Posts: 5866
Joined: Fri Jun 11, 2004 2:33 pm
Location: UC Berkeley
Contact:

Re: Zero-length model

Post by fmk » Mon Apr 08, 2013 12:47 pm

i suggest you clean up your model .. it is so full of stuff it makes no sense

e.g. nodes 1 through 5 are fixed yet ..
rigidLink bar 1 2;
rigidLink bar 2 3;
rigidLink bar 3 4;
rigidLink bar 4 5;

so the commands make no sense as the nodes are fixed anyway

also the other rigidLink commands also have no effect as the nodes only differ in the y dirn and you already have equalDOF commands!

as for those equalDOF commands, you are equalDOF'ing to nodes that are fixed. just use the fix command
i.e replace:

equalDOF 1 6 2 3;
equalDOF 2 7 2 3;
equalDOF 3 8 2 3;
equalDOF 4 9 2 3;
equalDOF 5 10 2 3;

with:
fix 6 0 1 1
fix 7 0 1 1
fix 8 0 1 1
fix 9 0 1 1
fix 10 0 1 1

node 11 obviously needs some constraints .. you have it connected via a truss to ONE other node and no constraints

after you sort out your boundary conditions you have to sort out the materials! replace the 5 and 8 materials with Elastic materials until you sort out your bondary conditions and then you can figure out what you did wrong with your materials!

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